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          <a href="./IO::Zlib.html">IO::Zlib</a>
          <div id="more">
            (<a href="./IO::Zlib.txt">source</a>,
            <a href="https://metacpan.org/pod/IO::Zlib">CPAN</a>)
          </div>
            <div id="moduleversion">version 1.11</div>
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        <div class="leading-notice">
          You are viewing the version of this documentation from Perl 5.35.0.
            This is a development version of Perl.
        </div>
        <h1><a id="toc">CONTENTS</a></h1>
                  <ul>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#NAME">NAME</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#SYNOPSIS">SYNOPSIS</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#DESCRIPTION">DESCRIPTION</a>
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              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#CONSTRUCTOR">CONSTRUCTOR</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#OBJECT-METHODS">OBJECT METHODS</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#USING-THE-EXTERNAL-GZIP">USING THE EXTERNAL GZIP</a>
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              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#CLASS-METHODS">CLASS METHODS</a>
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                <a class="text-decoration-none" href="./IO::Zlib.html#DIAGNOSTICS">DIAGNOSTICS</a>
              </li>
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                <a class="text-decoration-none" href="./IO::Zlib.html#SEE-ALSO">SEE ALSO</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#HISTORY">HISTORY</a>
              </li>
              <li>
                <a class="text-decoration-none" href="./IO::Zlib.html#COPYRIGHT">COPYRIGHT</a>
              </li>
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      <h1 id="NAME"><a class="permalink" href="./IO::Zlib.html#NAME">#</a>NAME</h1>

<p>IO::Zlib - IO:: style interface to <a href="./Compress::Zlib.html">Compress::Zlib</a></p>

<h1 id="SYNOPSIS"><a class="permalink" href="./IO::Zlib.html#SYNOPSIS">#</a>SYNOPSIS</h1>

<p>With any version of Perl 5 you can use the basic OO interface:</p>

<pre><code>use IO::Zlib;

$fh = new IO::Zlib;
if ($fh-&gt;open(&quot;file.gz&quot;, &quot;rb&quot;)) {
    print &lt;$fh&gt;;
    $fh-&gt;close;
}

$fh = IO::Zlib-&gt;new(&quot;file.gz&quot;, &quot;wb9&quot;);
if (defined $fh) {
    print $fh &quot;bar\n&quot;;
    $fh-&gt;close;
}

$fh = IO::Zlib-&gt;new(&quot;file.gz&quot;, &quot;rb&quot;);
if (defined $fh) {
    print &lt;$fh&gt;;
    undef $fh;       # automatically closes the file
}</code></pre>

<p>With Perl 5.004 you can also use the TIEHANDLE interface to access compressed files just like ordinary files:</p>

<pre><code>use IO::Zlib;

tie *FILE, &#39;IO::Zlib&#39;, &quot;file.gz&quot;, &quot;wb&quot;;
print FILE &quot;line 1\nline2\n&quot;;

tie *FILE, &#39;IO::Zlib&#39;, &quot;file.gz&quot;, &quot;rb&quot;;
while (&lt;FILE&gt;) { print &quot;LINE: &quot;, $_ };</code></pre>

<h1 id="DESCRIPTION"><a class="permalink" href="./IO::Zlib.html#DESCRIPTION">#</a>DESCRIPTION</h1>

<p><code>IO::Zlib</code> provides an IO:: style interface to <a href="./Compress::Zlib.html">Compress::Zlib</a> and hence to gzip/zlib compressed files. It provides many of the same methods as the <a href="./IO::Handle.html">IO::Handle</a> interface.</p>

<p>Starting from IO::Zlib version 1.02, IO::Zlib can also use an external <i>gzip</i> command. The default behaviour is to try to use an external <i>gzip</i> if no <code>Compress::Zlib</code> can be loaded, unless explicitly disabled by</p>

<pre><code>use IO::Zlib qw(:gzip_external 0);</code></pre>

<p>If explicitly enabled by</p>

<pre><code>use IO::Zlib qw(:gzip_external 1);</code></pre>

<p>then the external <i>gzip</i> is used <b>instead</b> of <code>Compress::Zlib</code>.</p>

<h1 id="CONSTRUCTOR"><a class="permalink" href="./IO::Zlib.html#CONSTRUCTOR">#</a>CONSTRUCTOR</h1>

<dl>

<dt id="new-(-[ARGS]-)"><a class="permalink" href="./IO::Zlib.html#new-(-%5BARGS%5D-)">#</a><a id="new"></a><a id="new-ARGS"></a>new ( [ARGS] )</dt>
<dd>

<p>Creates an <code>IO::Zlib</code> object. If it receives any parameters, they are passed to the method <code>open</code>; if the open fails, the object is destroyed. Otherwise, it is returned to the caller.</p>

</dd>
</dl>

<h1 id="OBJECT-METHODS"><a class="permalink" href="./IO::Zlib.html#OBJECT-METHODS">#</a><a id="OBJECT"></a>OBJECT METHODS</h1>

<dl>

<dt id="open-(-FILENAME,-MODE-)"><a class="permalink" href="./IO::Zlib.html#open-(-FILENAME,-MODE-)">#</a><a id="open"></a><a id="open-FILENAME-MODE"></a>open ( FILENAME, MODE )</dt>
<dd>

<p><code>open</code> takes two arguments. The first is the name of the file to open and the second is the open mode. The mode can be anything acceptable to <a href="./Compress::Zlib.html">Compress::Zlib</a> and by extension anything acceptable to <i>zlib</i> (that basically means POSIX fopen() style mode strings plus an optional number to indicate the compression level).</p>

</dd>
<dt id="opened"><a class="permalink" href="./IO::Zlib.html#opened">#</a>opened</dt>
<dd>

<p>Returns true if the object currently refers to a opened file.</p>

</dd>
<dt id="close"><a class="permalink" href="./IO::Zlib.html#close">#</a>close</dt>
<dd>

<p>Close the file associated with the object and disassociate the file from the handle. Done automatically on destroy.</p>

</dd>
<dt id="getc"><a class="permalink" href="./IO::Zlib.html#getc">#</a>getc</dt>
<dd>

<p>Return the next character from the file, or undef if none remain.</p>

</dd>
<dt id="getline"><a class="permalink" href="./IO::Zlib.html#getline">#</a>getline</dt>
<dd>

<p>Return the next line from the file, or undef on end of string. Can safely be called in an array context. Currently ignores $/ ($INPUT_RECORD_SEPARATOR or $RS when <a href="English.html">English</a> is in use) and treats lines as delimited by &quot;\n&quot;.</p>

</dd>
<dt id="getlines"><a class="permalink" href="./IO::Zlib.html#getlines">#</a>getlines</dt>
<dd>

<p>Get all remaining lines from the file. It will croak() if accidentally called in a scalar context.</p>

</dd>
<dt id="print-(-ARGS...-)"><a class="permalink" href="./IO::Zlib.html#print-(-ARGS...-)">#</a><a id="print"></a><a id="print-ARGS"></a>print ( ARGS... )</dt>
<dd>

<p>Print ARGS to the file.</p>

</dd>
<dt id="read-(-BUF,-NBYTES,-[OFFSET]-)"><a class="permalink" href="./IO::Zlib.html#read-(-BUF,-NBYTES,-%5BOFFSET%5D-)">#</a><a id="read"></a><a id="read-BUF-NBYTES-OFFSET"></a>read ( BUF, NBYTES, [OFFSET] )</dt>
<dd>

<p>Read some bytes from the file. Returns the number of bytes actually read, 0 on end-of-file, undef on error.</p>

</dd>
<dt id="eof"><a class="permalink" href="./IO::Zlib.html#eof">#</a>eof</dt>
<dd>

<p>Returns true if the handle is currently positioned at end of file?</p>

</dd>
<dt id="seek-(-OFFSET,-WHENCE-)"><a class="permalink" href="./IO::Zlib.html#seek-(-OFFSET,-WHENCE-)">#</a><a id="seek"></a><a id="seek-OFFSET-WHENCE"></a>seek ( OFFSET, WHENCE )</dt>
<dd>

<p>Seek to a given position in the stream. Not yet supported.</p>

</dd>
<dt id="tell"><a class="permalink" href="./IO::Zlib.html#tell">#</a>tell</dt>
<dd>

<p>Return the current position in the stream, as a numeric offset. Not yet supported.</p>

</dd>
<dt id="setpos-(-POS-)"><a class="permalink" href="./IO::Zlib.html#setpos-(-POS-)">#</a><a id="setpos"></a><a id="setpos-POS"></a>setpos ( POS )</dt>
<dd>

<p>Set the current position, using the opaque value returned by <code>getpos()</code>. Not yet supported.</p>

</dd>
<dt id="getpos-(-POS-)"><a class="permalink" href="./IO::Zlib.html#getpos-(-POS-)">#</a><a id="getpos"></a><a id="getpos-POS"></a>getpos ( POS )</dt>
<dd>

<p>Return the current position in the string, as an opaque object. Not yet supported.</p>

</dd>
</dl>

<h1 id="USING-THE-EXTERNAL-GZIP"><a class="permalink" href="./IO::Zlib.html#USING-THE-EXTERNAL-GZIP">#</a><a id="USING"></a>USING THE EXTERNAL GZIP</h1>

<p>If the external <i>gzip</i> is used, the following <code>open</code>s are used:</p>

<pre><code>open(FH, &quot;gzip -dc $filename |&quot;)  # for read opens
open(FH, &quot; | gzip &gt; $filename&quot;)   # for write opens</code></pre>

<p>You can modify the &#39;commands&#39; for example to hardwire an absolute path by e.g.</p>

<pre><code>use IO::Zlib &#39;:gzip_read_open&#39;  =&gt; &#39;/some/where/gunzip -c %s |&#39;;
use IO::Zlib &#39;:gzip_write_open&#39; =&gt; &#39;| /some/where/gzip.exe &gt; %s&#39;;</code></pre>

<p>The <code>%s</code> is expanded to be the filename (<code>sprintf</code> is used, so be careful to escape any other <code>%</code> signs). The &#39;commands&#39; are checked for sanity - they must contain the <code>%s</code>, and the read open must end with the pipe sign, and the write open must begin with the pipe sign.</p>

<h1 id="CLASS-METHODS"><a class="permalink" href="./IO::Zlib.html#CLASS-METHODS">#</a><a id="CLASS"></a>CLASS METHODS</h1>

<dl>

<dt id="has_Compress_Zlib"><a class="permalink" href="./IO::Zlib.html#has_Compress_Zlib">#</a>has_Compress_Zlib</dt>
<dd>

<p>Returns true if <code>Compress::Zlib</code> is available. Note that this does not mean that <code>Compress::Zlib</code> is being used: see <a href="./IO::Zlib.html#gzip_external">&quot;gzip_external&quot;</a> and <a href="https://perldoc.perl.org/5.35.0/gzip_used">gzip_used</a>.</p>

</dd>
<dt id="gzip_external"><a class="permalink" href="./IO::Zlib.html#gzip_external">#</a>gzip_external</dt>
<dd>

<p>Undef if an external <i>gzip</i> <b>can</b> be used if <code>Compress::Zlib</code> is not available (see <a href="./IO::Zlib.html#has_Compress_Zlib">&quot;has_Compress_Zlib&quot;</a>), true if an external <i>gzip</i> is explicitly used, false if an external <i>gzip</i> must not be used. See <a href="./IO::Zlib.html#gzip_used">&quot;gzip_used&quot;</a>.</p>

</dd>
<dt id="gzip_used"><a class="permalink" href="./IO::Zlib.html#gzip_used">#</a>gzip_used</dt>
<dd>

<p>True if an external <i>gzip</i> is being used, false if not.</p>

</dd>
<dt id="gzip_read_open"><a class="permalink" href="./IO::Zlib.html#gzip_read_open">#</a>gzip_read_open</dt>
<dd>

<p>Return the &#39;command&#39; being used for opening a file for reading using an external <i>gzip</i>.</p>

</dd>
<dt id="gzip_write_open"><a class="permalink" href="./IO::Zlib.html#gzip_write_open">#</a>gzip_write_open</dt>
<dd>

<p>Return the &#39;command&#39; being used for opening a file for writing using an external <i>gzip</i>.</p>

</dd>
</dl>

<h1 id="DIAGNOSTICS"><a class="permalink" href="./IO::Zlib.html#DIAGNOSTICS">#</a>DIAGNOSTICS</h1>

<dl>

<dt id="IO::Zlib::getlines:-must-be-called-in-list-context"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::getlines:-must-be-called-in-list-context">#</a><a id="IO"></a>IO::Zlib::getlines: must be called in list context</dt>
<dd>

<p>If you want read lines, you must read in list context.</p>

</dd>
<dt id="IO::Zlib::gzopen_external:-mode-&#39;...&#39;-is-illegal"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::gzopen_external:-mode-&#39;...&#39;-is-illegal">#</a><a id="IO1"></a><a id="IO::Zlib::gzopen_external:-mode-...-is-illegal"></a>IO::Zlib::gzopen_external: mode &#39;...&#39; is illegal</dt>
<dd>

<p>Use only modes &#39;rb&#39; or &#39;wb&#39; or /wb[1-9]/.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;...&#39;-is-illegal"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;...&#39;-is-illegal">#</a><a id="IO2"></a><a id="IO::Zlib::import:-...-is-illegal"></a>IO::Zlib::import: &#39;...&#39; is illegal</dt>
<dd>

<p>The known import symbols are the <code>:gzip_external</code>, <code>:gzip_read_open</code>, and <code>:gzip_write_open</code>. Anything else is not recognized.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;:gzip_external&#39;-requires-an-argument"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;:gzip_external&#39;-requires-an-argument">#</a><a id="IO3"></a><a id="IO::Zlib::import:-:gzip_external-requires-an-argument"></a>IO::Zlib::import: &#39;:gzip_external&#39; requires an argument</dt>
<dd>

<p>The <code>:gzip_external</code> requires one boolean argument.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;gzip_read_open&#39;-requires-an-argument"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;gzip_read_open&#39;-requires-an-argument">#</a><a id="IO4"></a><a id="IO::Zlib::import:-gzip_read_open-requires-an-argument"></a>IO::Zlib::import: &#39;gzip_read_open&#39; requires an argument</dt>
<dd>

<p>The <code>:gzip_external</code> requires one string argument.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;gzip_read&#39;-&#39;...&#39;-is-illegal"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;gzip_read&#39;-&#39;...&#39;-is-illegal">#</a><a id="IO5"></a><a id="IO::Zlib::import:-gzip_read-...-is-illegal"></a>IO::Zlib::import: &#39;gzip_read&#39; &#39;...&#39; is illegal</dt>
<dd>

<p>The <code>:gzip_read_open</code> argument must end with the pipe sign (|) and have the <code>%s</code> for the filename. See <a href="./IO::Zlib.html#USING-THE-EXTERNAL-GZIP">&quot;USING THE EXTERNAL GZIP&quot;</a>.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;gzip_write_open&#39;-requires-an-argument"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;gzip_write_open&#39;-requires-an-argument">#</a><a id="IO6"></a><a id="IO::Zlib::import:-gzip_write_open-requires-an-argument"></a>IO::Zlib::import: &#39;gzip_write_open&#39; requires an argument</dt>
<dd>

<p>The <code>:gzip_external</code> requires one string argument.</p>

</dd>
<dt id="IO::Zlib::import:-&#39;gzip_write_open&#39;-&#39;...&#39;-is-illegal"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-&#39;gzip_write_open&#39;-&#39;...&#39;-is-illegal">#</a><a id="IO7"></a><a id="IO::Zlib::import:-gzip_write_open-...-is-illegal"></a>IO::Zlib::import: &#39;gzip_write_open&#39; &#39;...&#39; is illegal</dt>
<dd>

<p>The <code>:gzip_write_open</code> argument must begin with the pipe sign (|) and have the <code>%s</code> for the filename. An output redirect (&gt;) is also often a good idea, depending on your operating system shell syntax. See <a href="./IO::Zlib.html#USING-THE-EXTERNAL-GZIP">&quot;USING THE EXTERNAL GZIP&quot;</a>.</p>

</dd>
<dt id="IO::Zlib::import:-no-Compress::Zlib-and-no-external-gzip"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::import:-no-Compress::Zlib-and-no-external-gzip">#</a><a id="IO8"></a>IO::Zlib::import: no Compress::Zlib and no external gzip</dt>
<dd>

<p>Given that we failed to load <code>Compress::Zlib</code> and that the use of an external <i>gzip</i> was disabled, IO::Zlib has not much chance of working.</p>

</dd>
<dt id="IO::Zlib::open:-needs-a-filename"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::open:-needs-a-filename">#</a><a id="IO9"></a>IO::Zlib::open: needs a filename</dt>
<dd>

<p>No filename, no open.</p>

</dd>
<dt id="IO::Zlib::READ:-NBYTES-must-be-specified"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::READ:-NBYTES-must-be-specified">#</a><a id="IO10"></a>IO::Zlib::READ: NBYTES must be specified</dt>
<dd>

<p>We must know how much to read.</p>

</dd>
<dt id="IO::Zlib::WRITE:-too-long-LENGTH"><a class="permalink" href="./IO::Zlib.html#IO::Zlib::WRITE:-too-long-LENGTH">#</a><a id="IO11"></a>IO::Zlib::WRITE: too long LENGTH</dt>
<dd>

<p>The LENGTH must be less than or equal to the buffer size.</p>

</dd>
</dl>

<h1 id="SEE-ALSO"><a class="permalink" href="./IO::Zlib.html#SEE-ALSO">#</a><a id="SEE"></a>SEE ALSO</h1>

<p><a href="perlfunc.html">perlfunc</a>, <a href="perlop.html#I%2FO-Operators">&quot;I/O Operators&quot; in perlop</a>, <a href="./IO::Handle.html">IO::Handle</a>, <a href="./Compress::Zlib.html">Compress::Zlib</a></p>

<h1 id="HISTORY"><a class="permalink" href="./IO::Zlib.html#HISTORY">#</a>HISTORY</h1>

<p>Created by Tom Hughes &lt;<i>tom@compton.nu</i>&gt;.</p>

<p>Support for external gzip added by Jarkko Hietaniemi &lt;<i>jhi@iki.fi</i>&gt;.</p>

<h1 id="COPYRIGHT"><a class="permalink" href="./IO::Zlib.html#COPYRIGHT">#</a>COPYRIGHT</h1>

<p>Copyright (c) 1998-2004 Tom Hughes &lt;<i>tom@compton.nu</i>&gt;. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.</p>


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